lkml.org 
[lkml]   [2009]   [Apr]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [rfc 2/2] x86, bts: use physically non-contiguous trace buffer
Markus Metzger wrote:
> Use vmalloc to allocate the branch trace buffer.
>
> Peter Zijlstra suggested to use vmalloc rather than kmalloc to
> allocate the potentially multi-page branch trace buffer.
>
> Is there a way to have vmalloc allocate a physically non-contiguous
> buffer for test purposes? Ideally, the memory area would have big
> holes in it with sensitive data in between so I would know immediately
> when this is overwritten.

For test purposes you could hack vmalloc.c to allocate more pages
and only put in every second/third/... into the mapping. You would
just need to add another to loop to __vmalloc_area_node() that allocates
more. That should give you non continuous mappings unless you're really unlucky.

-Andi


>
>
> Reported-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
> CC: Andrew Morton <akpm@linux-foundation.org>
> Signed-off-by: Markus Metzger <markus.t.metzger@intel.com>
> ---
> arch/x86/kernel/ptrace.c | 5 3 + 2 - 0 !
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> Index: b/arch/x86/kernel/ptrace.c
> ===================================================================
> --- a/arch/x86/kernel/ptrace.c
> +++ b/arch/x86/kernel/ptrace.c
> @@ -22,6 +22,7 @@
> #include <linux/seccomp.h>
> #include <linux/signal.h>
> #include <linux/workqueue.h>
> +#include <linux/vmalloc.h>
>
> #include <asm/uaccess.h>
> #include <asm/pgtable.h>
> @@ -626,7 +627,7 @@ static int alloc_bts_buffer(struct bts_c
> if (err < 0)
> return err;
>
> - buffer = kzalloc(size, GFP_KERNEL);
> + buffer = vmalloc(size);
> if (!buffer)
> goto out_refund;
>
> @@ -646,7 +647,7 @@ static inline void free_bts_buffer(struc
> if (!context->buffer)
> return;
>
> - kfree(context->buffer);
> + vfree(context->buffer);
> context->buffer = NULL;
>
> refund_locked_memory(context->mm, context->size);



\
 
 \ /
  Last update: 2009-04-25 08:43    [W:0.302 / U:0.484 seconds]
©2003-2014 Jasper Spaans. Advertise on this site